[[alternative]]A study on performance of PVDF hollow fiber in membrane distillation

碩士[[abstract]]本研究以實驗室合成之聚偏二氟乙烯(poly(vinylidene fluoride), PVDF)中空纖維膜組裝之模組進行真空式薄膜蒸餾(vacuum membrane distillation)及直接接觸式薄膜蒸餾(direct contact membrane distillation)實驗，進料溶液為3.5 wt%之鹽水溶液，操作參數為進料溫度(50~70 oC)及進料速率(0.1~0.4 L/min)，真空式薄膜蒸餾其真空度為持在8 kPa，直接接觸式薄膜蒸餾之冷水側溫度為17.5 oC及進料速率0.4 L/min。 製備中空纖維膜的條件為改變沉澱槽之組成，其中共五種條件分別為純水相及10、20、40、60 wt%磷酸三乙酯(TEP)水溶液，藉由硬性沉澱槽換成軟性沉澱槽的方式來改善中空纖維膜表面皮層結構。從SEM解析得知隨著磷酸三乙酯(TEP)在沉澱槽的比例增加薄膜表面皮層結構不易形成，且大孔洞數變多。 真空式及直接接觸式薄膜蒸餾操作中，提高進料溫度能明顯增加滲透通量，但極化現象也較嚴重，此外薄膜於真空式薄膜蒸餾會有fouling現象，造成氯化鈉顆粒析出於殼測薄膜表面，此種現象會造成薄膜之有效面積減少，降低純水通量。增加進料流率對於滲透通量之提升較不顯著，但對於高溫進料操作之溫度極化現象具有較明顯改善效果。 其結果顯示隨著沉澱槽TEP wt%的比例增加，所製成的薄膜在直接接觸式薄膜蒸餾有較高的通量，但在真空式薄膜蒸餾中較不明顯。孔洞較大的薄膜對於進料溫度及速率的增加在通量的提升效果高於小孔洞之薄膜。此外短模組在真空及直接接觸式薄膜蒸餾操作中的滲透通量都明顯高於長模組。[[abstract]]In this study, laboratory made poly(vinylidene fluoride), PVDF, hollow fiber membranes were used in vacuum and direct contact membrane distillation of saline solution. The feed solution was 3.5 wt% NaCl solution, the operating parameters included feed temperature (50 ~ 60 oC), feed rate (0.1 ~ 0.4 L / min), the vacuum pressure in the permeate side was controlled at 8 kPa for vacuum membrane distillation, and cooling water controlled at 17.5 oC with rate 0.4 L / min for direct contact membrane distillation. The hollow fiber membranes were prepared by varying the composition of the coagulation bath. There were five conditions, which water phase、10、20、40、60 wt% triethylphosphate (TEP) solution. The outer skin of the hollow fiber membrane was improved by changed the bath from hard coagulation (water bath) to soft coagulation. Analysis the structure by SEM morphology, which membrane have large pore size in the outer surface by increasing the weight percent of TEP in coagulant bath. In the vacuum and direct contact membrane distillation experiment, raising the temperature of the feed can significantly increase the flux, but the polarization phenomena become more serious. In addition, the membrane surface will have fouling phenomenon that NaCl was separated out to the shell side membrane surface in vacuum membrane distillation. This situation will cause decrease the effective area of the membrane and reduce the flux. Increasing feed flow rate has a finite effect on increasing the flux, but the temperature polarization phenomenon can be reduced by the feed flow rate as higher feed temperature. The experimental results showed the higher flux performance on direct contact membrane distillation which prepared by higher weigh percent of TEP coagulation bath solution but not obviously in the vacuum membrane distillation. The large pore size membrane flux which increased by higher inlet temperature more obvious then the small one. Furthermore, the short module have higher flux then long module in the same inlet condition.[[tableofcontents]]目錄 誌謝I 中文摘要II 英文摘要III 目錄IV 圖目錄VI 表目錄VIII 第一章緒論1 1.1前言1 1.2薄膜的應用2 1.3薄膜分離5 1.4薄膜蒸餾7 1.5研究之目地9 第二章文獻回顧13 2.1薄膜蒸餾法13 2.1.1直接接觸式薄膜蒸餾13 2.1.2空氣間隙式薄膜蒸餾14 2.1.3空氣掃掠式薄膜蒸餾14 2.1.4真空式薄膜蒸餾14 2.2殼管式模組15 2.3薄膜之孔隙結構及性質16 2.4影響滲透通量的因素18 2.5薄膜製備(相轉換法)20 2.6高分子成膜理論21 2.6.1成膜理論(熱力學)21 2.6.2成膜理論(質傳動力學)23 2.7PVDF中空纖維膜24 第三章實驗裝置與方法28 3.1薄膜製備28 3.1.1PVDF薄膜製備及解析28 3.1.2中空纖維模組製作及模組編號29 3.2BUBBLE POINT METHOD30 3.3薄膜孔隙度30 3.4VMD薄膜蒸餾31 3.5DCMD薄膜蒸餾32 3.6實驗設備及藥品33 第四章結果與討論42 4.1SEM解析探討42 4.2VMD 薄膜蒸餾45 4.2.1薄膜改質後在VMD實驗之探討45 4.2.2鹽水濃度之影響48 4.2.3膜組長度對於VMD之影響49 4.3DCMD 薄膜蒸餾50 4.3.1薄膜改質後在DCMD實驗之探討50 4.3.2膜組長度對於VMD之影響52 4.4VMD和DCMD兩系統比較53 4.5VMD和DCMD兩系統與文獻比較54 4.6薄膜阻隔率55 第五章結論72 參考文獻74 圖目錄 圖1.1薄膜分離程序之分類[Cheryan,1998]10 圖1.2PVDF10 圖1.3薄膜蒸餾物流流動示意圖[陳勝昌,2013]11 圖2.1薄膜蒸餾膜組之型式26 圖2.2高分子(非結晶型)-溶劑-非溶劑成膜相圖[Marcel Mulder, 1991] 27 圖2.3Schematic representation of mass transfer occurring at the membrane/coagulant surface[Marcel Mulder, 1991；Lin and Wang 等人,1996].27 圖3.1噴紡法製備毛細管薄膜之裝置示意圖35 圖3.2中空壓克力模組35 圖3.3DCMD與VMD模組設計示意圖36 圖3.4Bubble point experiment set up37 圖3.5VMD experiment set up38 圖3.6DCMD experiment set up38 圖4.1添加不同比例之TEP於沉澱槽澱槽70倍之薄膜截面56 圖4.2添加不同比例之TEP於沉澱槽澱槽400倍之薄膜截面57 圖4.3添加不同比例之TEP於沉澱槽澱槽10000倍之薄膜截面58 圖4.4添加不同比例之TEP於沉澱槽澱槽10000倍之薄膜內表面59 圖4.5添加不同比例之TEP於沉澱槽澱槽10000倍之薄膜外表面60 圖4.6鹽水於50~60oC&0.4 L/min進料速率下VMD之滲透通量61 圖4.7鹽水於50oC在不同進料速率下VMD之滲透通量61 圖4.8鹽水於60oC在不同進料速率下VMD之滲透通量62 圖4.9(60oC&0.4L/min)進料條件下鹽水濃度對VMD滲透通量的影響62 圖4.1015wt%鹽水(60oC&0.4 L/min)條件下對M-14-10-T60模組之影響63 圖4.11VMD實驗模組長度之影響63 圖4.12鹽水於50~70oC&0.4L/min進料速率下DCMD之滲透通量64 圖4.13鹽水於50oC在不同進料速率下DCMD之滲透通量64 圖4.14鹽水於60oC在不同進料速率下DCMD之滲透通量65 圖4.15鹽水於70oC在不同進料速率下DCMD之滲透通量65 圖4.16DCMD實驗T0、T10模組長度之影響66 圖4.17DCMD實驗T10模組長度之影響66 圖4.18模組於鹽水50oC&0.4L/min對VDM&DCMD之影響67 圖4.19模組於鹽水60oC&0.4L/min對VDM&DCMD之影響67 圖4.20模組於鹽水50oC&0.1~0.4L/min對VDM&DCMD之影響68 圖4.21模組於鹽水60oC&0.1~0.4L/min對VDM&DCMD之影響68 圖4.22T0薄膜於50oC進行兩天DCMD之通量及導電度69 圖4.23T60薄膜於50oC進行兩天DCMD之通量及導電度69 表目錄 表1.1不同操作程序之驅動力分類[Cheryan,1998]12 表3.1Process parameters/spinning condition39 表3.2中空纖維管之膜組規格40 表3.3Characteristic of hollow fiber module41 表4.1Characteristic of membrane in different coagulation bath70 表4.2VMD result compare with references70 表4.3DCMD result compare with references71[[note]]學號: 601400491, 學年度: 10